Modified lubricating oil



Patented Dec. 5, 1944 UNITED STATES PATENT OFFICE MODIFIED LUBRICATIN G OIL Herbert C. Freuler, Orinda. Calif., asslgnor to Union Oil Company of California, Los Angeiel, Calii'., a corporation of California No Drawing. Application June 17, 1941,

Serial N0. 398,459

This invention relates principally ing oils, but may be extended also to other forms of lubricants such as greases, the so-called liquid greases and the like. The obiectof the in vention is to produce lubricating oils and other lubricants having high film strength, good oiliness characteristics, resistance to oxidation and to corrosion as by inhibiting the development 01 oxidation and corrosive conditions in the lubrican-ts.

This application is a continuation-in-part of my priorapplication Serial No. 156,946, filed August 2, i937.

I have discovered that by the addition of minor proportions of oil-soluble metal salts of alkyl esters of thio acids of phosphorus to lubricating oils, with or without the addition of other agents to the oils such as soaps and the like for the purpose of imparting detergent properties or thickening the oils, the resistance of oils to oxidation is greatly imrproved by what appears to bean inhibiting action on the part of the metal salts of th thiophosphates. Also the tendency to corrosion of metals by reason of the presence of some types of addition agents introduced into compounded oils to impart extreme pressure characteristics, is inhibited by these metallic derivatives of the phosphorus acids. This may apply to lubrication of gears, internal combustion engines, and other metal parts. Also the mentioned phosphates exert an inhibiting action against the development of conditions which are corrosive to highly corrosion-sensitive bearings in internal combustion engines and the like, such as Diesel engines and highoutput aviation englnes. For example, some highly refined lubricating oils have a tendency toward the development, apparently by oxidation, of acids corrosive to Ibearings such as cadmium-silver and copperlead bearings while in use in intenal combustion engines. Also similar corrosive acids tend to develop in some compounded oils while in use. Examples are oils which contain various detergent soaps now used in Diesel engines and the like. These soaps normally are added to the oils to overcome valve and ring sticking and the like and to keep the pistons and ring grooves clean. Such soaps include the oil-soluble metal soaps of various carboxylic acids such as chlorinated and phenylated fatty acids, oil-soluble metal soaps of high molecular weight acids derived from the oxidation of highly parafllnic petroleum fractions such as highly refined lubricating oils, and the like. These soaps, which may 38 Claims. (CL 252-39) to lubricat soaps such as calcium, magnesium, barium, zinc,

wise resulting from such soaps, by employing from 0.1% to 1.0% or 2.0% of one of the present metal thiophosphates as an inhibitor. These salts may also be added to compounded oils other than those mentioned. Again, I may add corresponding proportions of one of these metal thiophosphates to a highly refined highly paraffinic mineral lubricating oil and similarly inhibit oxidation and the development or corrosive conditions. This control of corrosion may or may not be the same type of control as that resulting where chlorinated or sulfurized extreme pressure agents are added to lubricants. Similarly I may use the corresponding metal phosphates which have no sulfur content and are wholly of the oxy-phosphate type, to Control oxidation and corrosion.

My invention therefore resides primarily in the employment in compounded or in uncompounded mineral lubricating oils, of minor proportions of oil-soluble metal salts of the thio acids of phos phorus substituted with organic radicals such as alkyl radicals which tend to render the salt oilsoluble. In addition to alkyl groups, other or-v ganic substituents or sufficiently high molecular weight to render the salts oil-soluble may be employed, such as aryl radicals, alkaryl radicals manganese, iron, tin, bismuth, and thorium For example, for the purpose of producing a most desirable extreme pressure agent I have employed zinc salts of octyl and di-octyl thioiphosphates, and on an average about 1.0% thereof based on the oil in the case of lubricating oils, or total content if a grease, has been found very satisfactory. Other alkyls may (be employed as substituents,

be alkaline earth metal Soaps or heavy metal 56 particularly the heavier ones inasmuch as these render the salts oil soluble. Examplesare the heptyl, decyl, dodecyl or lauryl, oleyl and similar 'alkyl groups.

The corresponding or similar. metal phosphates free from sulfur, i. e., wholly ,oxy phosphates, are also included in the invention-as anti-oxidants and the like.

Salts of these-:producedffrom the various metal indicated are goodinhibitors of oxidation and of corrosive conditions otherwise: developed while in use, and are goodinhibitors or retarders .of

corrosive conditions'whichresult from the use of corrosiveoiliness agents'sand the like containing halogens and corrosive sulfur, forexample 'Thezincsalts have been found very desirable. in

the preparation of extreme pressure agents, :and calcium and barium saltsare veryzdesirable as oxidation and corrosion retarders.

Instead of alkylgroupsas solubilizing .constituents'phenylgroups. alkylated .phenyl group naphthalene and anthracene groups may be employed, togetherwithkindred aryl groups and phenol groups or octyl-substituted phenol or nalphthyl groups, or cresyl groups.

A specific example of this invention whichis particularly valuableas a high iillm strength and oiliness agent, and-which alsoimparts-some oxiwhen employing the agent. In addition tothis film strength increase, the oil is made much'more resistant to oxidation thanin its original state. Moreover, the metallic salts of the alkyl thiophosphates in proportions here indicated inhibit, to a marked degree, the corrosion of metals by oils which contain sulfur, chlorine, corrosive sulfur compounds, corrosive halogenated bodies, or

corrosive organic compounds containing sulfur or halogen. Where these corrosive materials are present in relatively large amounts somewhat more than 1.0% of alkyl thiophosphate may be used as necessary or desirable in accomplishing the desired end. Inaddition to the-use of lead o zinc octyl thiophosphate, other metal salts may be employed, and likewise otheralkyl thiophosphates of such metals may be used. Examples of such other metals are aluminum, calcium, magnesium and others herein indicated.

In referring to the content of 1.0% of the salt in the lubricating oil, it is not intended to convey the idea that this amount is critical. Varying proportions may be employed in mineral lubricating oils between any lower range sufficient to produce the desired increased film strength, or oxidation control, for example, 0.1%, up to a figure such as 20% beyond. which added material produces no appreciable increased effect. For example, 10% of lead or zinc dioctyl .thiophosphate in an appropriate mineral oil, produces a very valuable hypoid gear lubricant Blends containing about one percent of the salt entirely inhibit the corrosion which normally takes place upon copper and steel when strips .alkylatedaryl groups, such as amyl-substituted thereof areimmersed in the lubricant for sixteen hours at 180 F. with water present and in contact with the strips.

As an example ofthe'preparatlon of the alkyl thiophosphates, octyl thiophosphate has been "prepared readily byv adding powdered phosphorus pentasulflde tooctyl alcohol ina glassor ceramic similar temperatures with an excess of a pow- .dered metal or metallic oxide to form the corresponding metal derivative. For example, in order to prepar the zinc octyl -thlophosphate,

the material resulting from the treatment of octyl alcohol with phosphorus pentasulfldeis agiitate'd with powdered zinc or zinc oxide untilno "more of the metallic compound is dissolved.

:Similartpreparations can be made with other metals although' in most cases it is preferable to use the. metallic oxide. 'l'hexmetailicderivatives of octyl ithiophosphate and similar thiophos- .phates are easily soluble in'mlneral oils of both westernand eastern types (naphthenic andparrailinic) and the oil solutions are therefore readily prepared by mere introduction of the salt and subsequent mild agitation. The term octylthiophospha usedin this disclosure. may refer to either the diorthe mono-octyl thlophosphate, although it is the .di-octyl 'thiophosphate which is the principal product of the abovepreparation.

.This is usually true of .the other phosphates.

The specific material produced by the method above described showed rapid reaction with evolution of hydrogen sulfide when the temperature reached 250 F. The phosphorus 'pentasulnde had all gone into solution, that is had entered into'chemlcal combination, in about two hours.

.This material analyzed 18.1% sulfur and 9.3% phosphorus. This indicated a product of the fol- "lowing composition:

sn S=1 O.C|Hi1 There is some evidence of the presence of a mono-octyl thiophosphate which would have the formula:

Other possible combinations are:

V 2,864,984 or an oxy-thio-acid of phosphorus. Such a material could have the formula:

The metal salts of these thiophosphates produced by the method above described were prepared by mixing the described ester with an excess of the oxides of the respective metals, such as zinc, lead, copper, manganese, iron and tin,

and allowing the resultant mixtures to stand overnight at about 250 F. Upon decanting and filtering, light colored .viscous liquids were obtained except in the case of ironand manganese where the liquids were dark. 1

These various metal salts of the thiophosphate esters were blended in a highly solvent refined highly parafllnic western lubricating oil in the amount of about 1.0% of the ester to 99% of the oil, and tested on the well known Timken tester for extreme pressure characteristics. In each instance an increase in the film strength was noted as measured by the increase in load supported over that supported by the same oil untreated. Similar results were obtained by testing each of the materials in the same proportion in the same oil upon the S. A. E. extreme pressure lubricants tester.

Each of the above described blends was also subjected to a corrosion test and found to show definite inhibition of corrosion to metals, although some exhibited greater corrosion inhibiting properties than others. Similarly each blend was tested and found to possess distinct oxidation inhibiting properties in the oil.

As an example of the salts, i. e., the phosphates, and the preparation of such metal phosphates which are wholly oxy-phosphates and free from sulfur, the following is given. Octyl alcohol is reacted with powdered phosphorus pentoxide (P205) in a glass or ceramic container in suitable moi proportions under conditions similar to those above described for the preparation of the thiophosphates. The liquid product obtained is similarly treated with an excess of the powdered metal or metallic oxide required for the desired metal derivative. Other aliphatic alcohols within the range herein indicated may be produced in a similar manner using phosphorus pentoxide. By this procedure metalsalts of substituted oxy acids of phosphorus are produced which correspend with the thio-phosphates previously described. 3

For production of either the thio-phosphates or the p ty-Phosphates, the method may be such as that disclosed by the Christmann Patent 1,893,018 for making thio-phosphates using P285. P205 may be substituted for the P255 in making the oxy-phosphates.

The oxy-phosphates may be prepared from the various substituted oxy-acids of pentavalent phosphorus of the following-and similar types:

wherein R and R will be alkyl, aryl, aik-aryl or ar-alkyl groups such as previously indicated which are-suiliciently heavyin carbon atoms to render the eventual salts sufficiently oil-soluble. R and R maybe the same or different groups.

These substituted oxy-acids of phosphorus may be prepared by any of the various methods known in the art. For example the method of the Graves Patent 2,005,619 using phosphorus oxychloride (POCls) may be employed. .Here the al- 1 cohol, with or without a solvent such as benzene, is heated in an acid-resistant vessel with a reflux condenser at reduced pressure to a temperature in the order of 30 C., or from 0 C.'to 100 C. and the phosphorus oxy-chloride is gradually introduced in liquid or vapor form, the liberated hydrogen chloride being largely removed as 1 formed. For'the present purpose I may use the esters, or" mixed esters, or mixtures of esters oi the various acids of phosphorus, namely orthophosphoric acid, meta-phosphoric acid, pyrophosphoric acid, phosphorous acid, and hypophosphorous acid, as disclosed by Graves. Oilsoluble metal salts of these esters may be prepared in any suitable manner such as indicated herein. Thus I may use oil-soluble di-octyl phosphate of one of the alkaline earth metals, or the di-decyl phosphate, or an oil-soluble alkaline earth metal octyl-decyl phosphate, such as the ortho-phosphate.

In general the alkyl groups employed will contain from aroundeight to around twenty carbons per molecule to insure sufilcient oil-solubility. Again the aromatic or ring compounds may be employed, these being used in suificient number per molecule, or in form modified by an alkyl, to insure oil-solubility.

According to another method for the preparation of the substituted oxy-acids of phosphorus, a mixture of an alcohol of the required type (higher alcohol) such as octyl alcohol, or phenol, or cresol, or alkylated phenol, with phosphorus pentoxide in ethyl ether is refluxed for several hours. This produces an alkyl-phosphoric acid which is soluble in the ether. The ether solution is decanted from any insolubles and the alkylphosphoric acid recovered. -Where the ethyl may b eliminated by hydrolysis.

Appropriate metal salts of the various substigroup enters into the alkyl-phosphoric acid it Z tuted oxy-acids of phosphorus thus obtained may be conveniently prepared by reacting the acid with sodium or potassium hydroxide, and then precipitating the desired metal salt from the solution by the addition of a suitable metal compound such as a calcium salt or aluminum salt. Also, the desired phosphate may be prepared from the substituted oxy-acids by direct neutralization, for example, with zinc oxide or with lime, according to the salt finally desired. Salts of the alkaline :earth metals, calcium, barium, strontium, lithium and magnesium, are valuable, as are those of zinc, lead, chromium, bismuth, thorium, aluminum, copper, iron, tin, manganese and the like herein mentioned. 1

The various salts so prepared from the substituted oxy-acids as justgiv'en and the various thio-salts previously described are adequately soluble in mineral lubricating oils, and are used according to this invention to control the sticking of piston rings and the like and also to control ,otli'er oxidation efiects and tendencies to develop corrosive conditions in lubricating oils when used in internal combustion engines and the like, especially severe service engines such as Diesel engines. Calcium and zinc dioctyl phosphates and oleyl andlauryl phosphates are good examples. I i

The proportions of the salts both of the straight oxy-materials free tromsulfur and of the thiomaterials used in lubricating oils will be similar valentphosphorus having an organic substituenttherein, said saltbeing present in an amount and in the orderof those previously indicated." 7

For example around 1.0% probably will be commonly used although proportions between about 0.5% and 2.0% will be in order and possibly for some uses as low as 0.1% or 0.2% or perhaps 'ashigha's3% or4%.

With respect to the various salts herein disclosed as additives for lubricating oils, possibly the alkaline earth metal salts are somewhat preferable to the other salts as anti-oxidants or corroslon inhibitors, and the salts of the other metals are possiblypreferable as extreme pressure agents. I 1

I claim: i

1. A composition of matter comprising a hydrocarbon, oil subjectto deterioration at elevated temperature, and an alkaline earth metal salt of a sulfur-containing substituted acid of phosphorus having an organic substitutent therein, said salt being present in an amount sufllcient substantially to inhibit said deterioration.

2. A composition of matter comprising a hydro- Y said deterioration.

carbon oil subject to deterioration at elevated temperature, and a calcium salt of a sulfur-containing substituted acid of phosphorus having an organic substituent therein, said salt being present in an amount sufflcient substantially to inhibit said deterioration.

3. A composition of matter comprising a hydrocarbon oil subject to deterioration at elevated temperature, anda magnesium salt of a sulfurcontaining substituted acid of phosphorushaving an organic substituent therein, said salt being present in an amount sufiicient substantially .to inhibit said deterioration.

4. A composition of matter comprising a hydrocarbon oil subject to deterioration at elevated temperature, and an-alkaline earth metal salt of a sulfur-containing substituted acid of' pentavalent phosphorus having an organic substituent therein, said salt being present in an amount sumcient substantially to inhibit said deterioration. I I

sufilcient substantially to stabilize said oil against deterioration during use.

9. A composition of matter comprising a hydrocarbon oil subject to deterioration in the presence of oxygen, and an alkaline earth metal salt of a thio-ester of phosphoric acid, said salt being present in an amount sufllcient substantially to inhibit said deterioration.

10. A composition of mattercomprising a hydrocarbon oil subject to deterioration in the presence of oxygen, and a calcium salt of a thioester of phosphoric acid, said salt being present in an amount suiilcient substantially to inhibit 11. A composition'of matter comprising a, hydrocarbon oil subject to deterioration in the presence of oxygen, and a magnesium salt of a thioester of phosphoric acid, said salt beingv present in an amount sufficient substantially to inhibit said deterioration.

12. A composition of matter comprisinga hydrocarbon oil subject to deterioration in the presence of oxygen, and an alkaline earth metal salt of an ester of a thiophosphoric' acid, said salt being present in an amount suflicient substantially to inhibit said deterioration.

13. A composition of matter comprising a hydrocarbon oil subject to deterioration in"the"" H inhibit said deterioration.

15. A composition or matter comprising a hydrocarbon oil subject to deterioration in the presence of oxygen and an alkaline earth metall salt of a thio-ester of a thin-phosphoric acid, said salt being present in an amount sufficient substantially to inhibit said deterioration.

16. A composition of matter comprising a hydrocarbon oil subject to deterioration in the 5. A composition of matter comprising a hydro- 1 carbon oil subject to deterioration at=elevated temperature, and a calcium salt of a sulfur-containing substituted acid of pentavalent phosphorus having an organic substituent therein, said salt being present in an amount sufficient substantially to inhibit said deterioration.

6. A composition of matter comprising a hydrocarbon oil subject to deterioration atelevated temperature, and a magnesium salt of a sulfurcontaining substituted acid of pentavalent phosphorus having an organic substituent therein, said salt being present in an amount suflicient substantially to inhibit said deterioration.

7. A stabilized liquid lubricant comprising a lubricating oil and an alkaline earth metal salt of a sulfur-containing substituted acid of phossaid salt being present in an amount sufilcient presence of oxygen and a calcium salt of a thioester of a thiophosphoric acid, said salt being present in-an amount sumcient substantially to inhibit said deterioration. I

17. A composition of matter'comprisinga hydrocarbon oil subject to deterioration in the presence of oxygen and a magnesium salt of a thioester of a thiophosphoric acid, said salt being present in an amount sufilcient substantially I to inhibit said deterioration.

18. A stabilized liquid lubricant comprising a parafilnic lubricating oil subject to deterioration at elevated temperature and more than approximately 0.1% b weight based on the oil of a magnesium salt 01' a sulfur containing substituted acid of phosphorus having an organic substituent therein in an amount sufficient substantially to inhibit said deterioration.

19. A stabilized liquid lubricant comprising a parafiinic lubricating oil subject to deterioration at elevated temperature and more than approximately 0.1% by weight based on the oil of an alkaline earth metal salt of a sulfur-containin substituted acid of phosphorus having an organic substituent therein in an amount sufficient substantially to inhibit said deterioration.

20. A stabilized liquid lubricant comprising a paraflinic lubricating oil subject to deterioration at elevated temperature and more than approximately 0.1% by weight based on the oil of a calcium salt of a sulfur-containing substituted acid of phosphorus having an organic substituent therein in an amount sufllcient substantially to inhibit said deterioration.

21. A composition of matter comprising a hydrocarbon oil subject to deterioration at elevated temperature and an alkaline earth metal salt of a sulfur containing substituted acid of phosphorus having an organic substituent of 8 carbon atoms therein, said salt being present in an amount suflicient substantiall to inhibit said drocarbon oil subject to deterioration at elevated temperature and a calcium salt of a sulfur containing substituted acid of phosphorus having an organic substituent of 8 carbon atoms therein in an amount suflicient substantially to inhibit said deterioration.

23. A composition of matter comprising a hydrocarbon oil subject to deterioration at elevated temperature and a magnesium salt of a sulfur containing substituted acid of phosphorus having an organic substituent of 8 carbon atoms therein in an amount sumcient substantially to inhibit said deterioration.

24. A stabilized liquid lubricant comprising a lubricating oil subject to deterioration at elevated temperature and more than approximately 0.10% by weight based on the oil of an alkaline earth metal salt of a sulfur containing substituted acid of phosphorus having at least one organic substituent of 8 carbon atoms therein in an amount sufllcient substantially to inhibit said deterioration.

25. A composition comprising a hydrocarbon oil subject to deterioration at elevated temperatures and an oil-soluble alkaline earth metal salt of an octyl thiophosphate, said salt being present in an amount suflicient substantially to inhibit said deterioration.

26. A composition of matter comprising a hydrocarbon oil subject to deterioration at elevated temperatures and an alkaline earth metal salt of a sulfur containing substituted acid of pentavalent phosphorus having two organic substituents therein, said salt being present in an amount sufflcient substantially to inhibit said deterioration.

27. A composition of matter comprising a hydrocarbon oil subject to deterioration at elevated temperature and a calcium salt of a sulfur containing substituted acid of pentavalent phosphorus having an organic substituent therein in an amount suflicient substantially to inhibit said deterioration.

28. A composition of matter comprising a hydrocarbon oil subject to deterioration at elevated temperature and a magnesium salt of a sulfur containing substituted acid of pentavalent phosphorus having two organic substituents therein in an amount suflicient substantially to inhibit said deterioration.

29. A composition comprising a hydrocarbon oil subject to deterioration at elevated temperatures and an oil-soluble alkaline earth metal salt of a di-octyl thiophosphate, said salt bein present in an amount sufiicient substantially to inhibit said deterioration.

30. A compounded lubricant comprising a lubricating oil subject to deterioration at elevated temperature and an alkaline earth metal salt of a sulfur-containing substituted acid of pentavalent phosphorus having more than approximately twelve carbon atoms in the molecule in an amount sufficient substantially to inhibit said deterioration.

31. A compounded lubricant comprising a lubricating oil subject to deterioration at elevated temperature and from approximately 0.1% to approximately 2% by weight based on the oil of a calcium salt of a sulfur-containing substituted acid of pentavalent phosphorus having more than approximately twelve carbon atoms in the molecule in an amount sufiicient substantially to inhibit said deterioration.

32. A compounded lubricant comprising a lubricating oil subject to deterioration at elevated temperature and from approximately 0.1% to approximately 2% by weight based on the oil of a magnesium salt of a sulfur-containing substituted acid of pentavalent phosphorus having more than approximately twelve carbon atoms in the molecule in an amount sufiicient substantially to inhibit said deterioration.

33. A lubricating oil containing a constituent corrosive to metal of the class consisting of sulfur. chlorine, sulfurized bodies, halogenated compounds, and metal corrosive organic compounds containing sulfur and halogens, and an oil-soluble alkaline earth metal salt of a sulfur containing substituted acid of phosphorus having an organic substituent therein, said salt bein present in an amount sufflcient to reduce oxidation and corrosion.

34. A composition of matter as claimed in claim 4, in which the sulfur containing substituted acid of pentavalent phosphorus having an organic substituent employed to produce the alkaline earth metal salt is obtained by reacting phosphorus pentasulfide with an alcohol.

35. A composition of matter as claimed in claim 5, in which the sulfur containing substituted acid of pentavalent phosphorus having an organic substituent employed to produce the calcium salt is obtained by reacting phosphorus pentasulfide with an alcohol.

36. A composition of matter as claimed in claim 6, in which the sulfur containing substituted acid of pentavalent phosphorus having an organic substituent employed to produce the magnesium salt is obtained by reacting phosphorus pentasulfide with an alcohol.

37. A composition of matter as claimed in claim 4, in which the sulfur containing substituted acid of pentavalent phosphorus having an organic substituent employed to produce the alkaline earth metal salt is obtained by reacting phosphorus pentasulflde with an aliphatic alcohol.

38. A composition of matter as claimed in claim 4, in which the sulfur containing substituted acid of pentavalent phosphorus having an organic substituent employed to produce the alkaline earth metal salt is obtained by reacting phosphorus pentasulflde with an octyl alcohol.

HERBERT C. FRE'ULER.

, 7 CERTIFICATE OF CORRECTION. 7 Patent No. 2,56lh28h. V December 5, 19141;.

' HEQRBERT I c FREULER.

It is hereby eer-tified that error appears in the printed specification of the abeve numbered patent requiring correction as follows: Page 1', first cOlunin line 11.0, for "intenal" read --in ternaI--; page 5, fipstcolumn, line 7 for 'any" reed -an--; page 5, first column, line 65, claim 27;

fer "an erganic s ubstituent" read -two organic subst1tuents--; andrth tr the said Letters Patent should be-read with this correction therein that the same may conferm to the record of the case in the Patent Office.

signed and sealed this 20th day of March, A. D. 19L 5;

, Leslie Frazer (Seal) 7 Aeting Commissioner of Patents. 

